serialization / deserialization of elkrem built, untested
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Tadge Dryja
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a3f65bb4ad
@ -37,13 +37,13 @@ to compute a previous index, compute at most h hashes.
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// You can calculate h from i but I can't figure out how without taking
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// O(i) ops. Feels like there should be a clever O(h) way. 1 byte, whatever.
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type ElkremNode struct {
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i uint64 // index (ith node)
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h uint8 // height of this node
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i uint64 // index (ith node)
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sha *wire.ShaHash // hash
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}
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type ElkremSender struct {
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current uint64 // last sent hash index
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treeHeight uint8 // height of tree (size is 2**height -1 )
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current uint64 // last sent hash index
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maxIndex uint64 // top of the tree
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root *wire.ShaHash // root hash of the tree
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}
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245
elkrem/serdes.go
245
elkrem/serdes.go
@ -4,38 +4,31 @@ import (
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"bytes"
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"encoding/binary"
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"fmt"
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"github.com/btcsuite/btcd/wire"
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)
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//type ElkremNode struct {
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// i uint64 // index (ith node)
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// h uint8 // height of this node
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// sha *wire.ShaHash // hash
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//}
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//type ElkremSender struct {
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// current uint64 // last sent hash index
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// treeHeight uint8 // height of tree (size is 2**height -1 )
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// maxIndex uint64 // top of the tree
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// root *wire.ShaHash // root hash of the tree
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//}
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//type ElkremReceiver struct {
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// current uint64 // last received index (actually don't need it?)
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// treeHeight uint8 // height of tree (size is 2**height -1 )
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// s []ElkremNode // store of received hashes, max size = height
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//}
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/* Serialization and Deserialization methods for the Elkrem structs.
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Senders turn into 41 byte long slices. Receivers are variable length,
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with 41 bytes for each stored hash, up to a maximum of 64. Receivers are
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prepended with the total number of hashes, so the total max size is 2625 bytes.
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*/
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// ToBytes turns an ElkremNode into a 41 byte long byte slice.
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// 8 byte index, 1 byte height, 32 byte hash
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// 1 byte height, 8 byte index, 32 byte hash
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func (e *ElkremNode) ToBytes() ([]byte, error) {
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var buf bytes.Buffer
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err := binary.Write(&buf, binary.BigEndian, e.i)
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// write 1 byte height
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err := binary.Write(&buf, binary.BigEndian, e.h)
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if err != nil {
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return nil, err
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}
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err = binary.Write(&buf, binary.BigEndian, e.h)
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// write 8 byte index
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err = binary.Write(&buf, binary.BigEndian, e.i)
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if err != nil {
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return nil, err
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}
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// write 32 byte sha hash
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n, err := buf.Write(e.sha.Bytes())
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if err != nil {
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return nil, err
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@ -47,26 +40,220 @@ func (e *ElkremNode) ToBytes() ([]byte, error) {
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return buf.Bytes(), nil
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}
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// FromBytes turns an ElkremNode into a 41 byte long byte slice.
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// 8 byte index, 1 byte height, 32 byte hash
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func ElkremNodeFromBytes([]byte) (ElkremNode, error) {
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// ElkremNodeFromBytes turns a 41 byte long byte slice into an ElkremNode.
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// 1 byte height, 8 byte index, 32 byte hash.
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func ElkremNodeFromBytes(b []byte) (ElkremNode, error) {
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var e ElkremNode
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buf := bytes.NewBuffer(b)
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// read 1 byte height
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err := binary.Read(buf, binary.BigEndian, &e.h)
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if err != nil {
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return e, err
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}
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// read 8 byte index
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err = binary.Read(buf, binary.BigEndian, &e.i)
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if err != nil {
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return e, err
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}
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// read 32 byte sha hash
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err = e.sha.SetBytes(buf.Next(32))
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if err != nil {
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return e, err
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}
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// sanity check. Node that this doesn't check that index and height
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// match. Could add that but it's slow.
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if e.h > 63 { // check for super high nodes
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return e, fmt.Errorf("Read invalid node height %d", e.h)
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}
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var max uint64 // maximum possible given height
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for j := uint8(0); j <= e.h; j++ {
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max = max<<1 | 1
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}
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if e.i > max-1 { // check for index higher than height allows
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return e, fmt.Errorf("Node claims index %d; %d max at height %d",
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e.i, max-1, e.h)
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}
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return e, nil
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}
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// ToBytes turns the Elkrem Sender into a 41 byte slice:
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// first the tree height (1 byte), then 8 byte index of last sent,
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// then the 32 byte root sha hash.
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func (e *ElkremSender) ToBytes() ([]byte, error) {
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var buf bytes.Buffer
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// write 1 byte height of tree (size of the whole sender)
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err := binary.Write(&buf, binary.BigEndian, e.treeHeight)
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if err != nil {
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return nil, err
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}
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// write 8 byte index of current sha (last sent)
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err = binary.Write(&buf, binary.BigEndian, e.current)
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if err != nil {
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return nil, err
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}
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// write 32 byte sha hash
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n, err := buf.Write(e.root.Bytes())
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if err != nil {
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return nil, err
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}
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if n != 32 {
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return nil, fmt.Errorf("%d byte hash, expect 32", n)
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}
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return nil, nil
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}
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func (e *ElkremSender) FromBytes([]byte) error {
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return nil
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// ElkremSenderFromBytes turns a 41 byte slice into a sender, picking up at
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// the index where it left off.
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func ElkremSenderFromBytes(b []byte) (ElkremSender, error) {
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var e ElkremSender
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buf := bytes.NewBuffer(b)
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// read 1 byte height
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err := binary.Read(buf, binary.BigEndian, &e.treeHeight)
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if err != nil {
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return e, err
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}
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// read 8 byte index
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err = binary.Read(buf, binary.BigEndian, &e.current)
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if err != nil {
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return e, err
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}
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// read 32 byte sha root
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err = e.root.SetBytes(buf.Next(32))
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if err != nil {
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return e, err
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}
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if e.treeHeight < 1 || e.treeHeight > 63 { // check for super high / low tree
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return e, fmt.Errorf("Read invalid sender tree height %d", e.treeHeight)
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}
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for j := uint8(0); j <= e.treeHeight; j++ {
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e.maxIndex = e.maxIndex<<1 | 1
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}
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e.maxIndex--
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if e.current > e.maxIndex { // check for index higher than height allows
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return e, fmt.Errorf("Sender claims current %d; %d max with height %d",
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e.current, e.maxIndex, e.treeHeight)
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}
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return e, nil
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}
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// ToBytes turns the Elkrem Receiver into a bunch of bytes in a slice.
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// first the tree height (1 byte), then number of nodes (1 byte),
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// then a series of 41 byte long serialized nodes,
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// which are 1 byte height, 8 byte index, 32 byte hash.
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func (e *ElkremReceiver) ToBytes() ([]byte, error) {
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return nil, nil
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numOfNodes := uint8(len(e.s))
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if numOfNodes == 0 {
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return nil, fmt.Errorf("Can't serialize empty ElkremReceiver")
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}
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if numOfNodes > 64 {
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return nil, fmt.Errorf("Broken ElkremReceiver has %d nodes, max 64",
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len(e.s))
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}
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var buf bytes.Buffer // create buffer
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// write tree height (1 byte)
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err := binary.Write(&buf, binary.BigEndian, e.treeHeight)
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if err != nil {
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return nil, err
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}
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// write number of nodes (1 byte)
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err = binary.Write(&buf, binary.BigEndian, numOfNodes)
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if err != nil {
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return nil, err
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}
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for _, node := range e.s {
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// write 1 byte height
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err = binary.Write(&buf, binary.BigEndian, node.h)
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if err != nil {
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return nil, err
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}
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// write 8 byte index
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err = binary.Write(&buf, binary.BigEndian, node.i)
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if err != nil {
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return nil, err
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}
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// write 32 byte sha hash
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n, err := buf.Write(node.sha.Bytes())
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if err != nil {
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return nil, err
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}
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if n != 32 { // make sure that was 32 bytes
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return nil, fmt.Errorf("%d byte hash, expect 32", n)
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}
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}
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if buf.Len() != (int(numOfNodes)*41)+2 {
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return nil, fmt.Errorf("Somehow made wrong size buf, got %d expect %d",
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buf.Len(), (numOfNodes*41)+2)
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}
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return buf.Bytes(), nil
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}
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func (e *ElkremReceiver) FromBytes([]byte) error {
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return nil
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func ElkremReceiverFromBytes(b []byte) (ElkremReceiver, error) {
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var e ElkremReceiver
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var numOfNodes uint8
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buf := bytes.NewBuffer(b)
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// read 1 byte tree height
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err := binary.Read(buf, binary.BigEndian, &e.treeHeight)
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if err != nil {
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return e, err
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}
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if e.treeHeight < 1 || e.treeHeight > 63 {
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return e, fmt.Errorf("Read invalid receiver height: %d", e.treeHeight)
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}
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var max uint64 // maximum possible given height
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for j := uint8(0); j <= e.treeHeight; j++ {
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max = max<<1 | 1
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}
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max--
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// read 1 byte number of nodes stored in receiver
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err = binary.Read(buf, binary.BigEndian, &numOfNodes)
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if err != nil {
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return e, err
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}
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if numOfNodes < 1 || numOfNodes > 64 {
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return e, fmt.Errorf("Read invalid number of nodes: %d", numOfNodes)
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}
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if buf.Len() != (int(numOfNodes)*41)+2 {
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return e, fmt.Errorf("Input buf wrong size, expect %d got %d",
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(numOfNodes*41)+2, buf.Len())
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}
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for i := uint8(0); i < numOfNodes; i++ {
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var node ElkremNode
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node.sha = new(wire.ShaHash)
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// read 1 byte height
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err := binary.Read(buf, binary.BigEndian, &node.h)
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if err != nil {
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return e, err
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}
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// read 8 byte index
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err = binary.Read(buf, binary.BigEndian, &node.i)
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if err != nil {
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return e, err
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}
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// read 32 byte sha hash
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err = node.sha.SetBytes(buf.Next(32))
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if err != nil {
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return e, err
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}
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// sanity check. Note that this doesn't check that index and height
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// match. Could add that but it's slow.
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if node.h > 63 { // check for super high nodes
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return e, fmt.Errorf("Read invalid node height %d", node.h)
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}
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if node.i > max { // check for index higher than height allows
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return e, fmt.Errorf("Node claims index %d; %d max at height %d",
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node.i, max, node.h)
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}
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e.s = append(e.s, node)
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if i > 0 { // check that node heights are descending
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if e.s[i-1].h < e.s[i].h {
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return e, fmt.Errorf("Node heights out of order")
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}
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}
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}
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return e, nil
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}
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